1. Field of Invention
This invention relates to a moving mirror support device for use in, for example, photo-interferometers, and more particularly, to an improvement therein for improving operation thereof.
2. Description of the Prior Art
In spectral analyzers or various measuring instruments using photo-interferometers, moving accuracy of the order of .mu.m is required of the moving mirror support device. However, if such instruments are used at a plant site, there is the problem of inability to attain high accuracy of measurement due to various environmental influences, such as vibration. In order to solve this problem, in the prior art, the rigidity of a moving mirror support device in directions other than the moving direction thereof was enhanced by arranging a pair of leaf springs to be parallel to each other.
FIG. 1 shows a Michelson interferometer, which is commonly used as a spectrometer in a spectral analyzer, wherein a light beam from light source 1 is changed to a parallel light by collimating lens 2, then divided into two directions with beam splitter 3. Moving mirror 4 and fixed mirror 5 return each light beam back to beam splitter 3 in opposite directions, and the return light beams are superimposed on beam splitter 3. The physical properties of the measured object (not shown) are measured by using the optical interference generated by the superimposed light beams.
FIG. 2(a) shows a conventional support device for a moving mirror used in such an interferometer, wherein moving mirror 4 is suspended from an upper position by two leaf springs 11 mounted on base 10 parallel to each other. Suspension by two leaf springs can suppress rotational motion generated when the moving mirror 4 is operated. If such an interferometer is used in a spectral analyzer, the moving mirror is driven transversely by a voice coil motor (not shown) about 0.3 mm and at 8 Hz. In such case, it is necessary to increase the amplitude (i.e. movement in the transverse direction) of the moving mirror in order to improve the resolution of the analyzer. However, by increasing the amplitude of the moving mirror 4, deformation of the two leaf springs 11 becomes large, as shown in FIG. 2(b), and the moving mirror is displaced transversely and longitudinally. Thus, the problem of longitudinal displacement arises and the optical axis of the return light will be shifted.